   messages added."
   [world :- WorldSchema
    new-messages :- [MessageEnvelopeSchema]]
-  (update-in world [:message-envelopes] concatv new-messages))
+  (update-in world [:message-envelopes] util/concatv new-messages))
 
 (s/defn get-node-from-world :- NetworkedNodeSchema
   [world :- WorldSchema

  "
  (:require [clojure.string :as str]
            [taoensso.timbre :as timbre]
            [schema.core :as s]))

(s/set-fn-validation! true)


               :receive-msg-node-unsubscription
               :replacement-messages replacement-messages
               :drop-me-msgs drop-me-msgs)
      [(node->removed node) (util/concatv replacement-messages drop-me-msgs)])))

(s/defmethod receive-msg :node-removal :- CommUpdateSchema
  #_"Take 'config, a 'node, and the contact address of a
